mod_timer: Add clarifying comments
Created by: AhmedImbabyGadallah
The timer module depends on the timer driver to enable and disable the timer's interrupt source, however the timer module is the one that clears the interrupt flag.
This behavior is explained in the timer driver API to avoid ambiguity for timer driver developers.
Signed-off-by: Ahmed Gadallah ahmed.gadallah@arm.com Change-Id: I982a9bffd3618c6b514e280e4601d4a58a9ce34a